Method of making high explosive shells



Jan. 4, 1944. LEFERE METHOD OF MAKING HIGH EXPLOSIVE SHELLS Filed April 30, 1941- ALIDUR 'LEFERE- a3, WW

- abto'z wngi Patented Jan. 4, 1944 METHOD or MAKING men I r 1 Sm Alidor Lefere, Jackson, Mich., assignor to Lefere Forge & Machine Companmlackson, Mich, a

- corporation of Michigan Application April 30, 1941, Serial No. 391,084

13 Claims.

The present invention relates to the production of relatively heavy tubular articles having closed ends, and more particularly to high explosiveshells.

Heretofore high explosive shells have generally been produced commercially by forcing a mandrel through a steel billet to provide atubular blank having a closed end. An attempt to forge I had a better grain structure than shells provided bythe said old method but also there was one end thereof closed, by directing water into a smaller waste of metal due to the fact that the manufacturing tolerances necessary for manufacturing shells according to my aforesaid invention were considerably closer than those origi nally required. It will be readily understood that the closer the manufacturing tolerances, the less the'machim'ng required for a finished shell and thus the smaller amount of metal machined away. As pointed out in my aforesaid patent, it is desirable that high explosive shells break into a large number. of small pieces. The fragmentation of a shell upon explosion is dependent largely upon the grain structure of the shell. By forging, according to the present method, I have produced a shell of a grain structure which will break into a large number of small pieces of substantially uniform size. According to the present invention, not only is the character of the grain structure controlled but also'the direction of alignment of the grains at the closed end of the shell is made such that there is a maximum fragmentation at the closed end. Another criterion of good fragmentation is freedom from scale during the various fabrication steps, for scale embedded in the surface of the shell blank during its manufacture will produce imperfections in the metal which will decrease the fragmentation. According to the present invention, shells or the like may be forged free from scale.

An object of the present invention is to provide a high. explosive shell or the like having a grain structure such that upon explosion the shell will break into a large number of pieces.

Another object of the invention is to provide, by pressure, a centering notch in a heated slug. Still another object of the invetnion is to squeeze a heated slug prior to forging to crack the scale therefrom.

Still another object of the invention is to provide a hollow tubular body, having one end closed by pressing a plug in one end of the same, forging,drawing, and pressure shaping.

Still another object of the invention is to remove scale from the forged; tubular body havin the open end of the body.

These and otherobjects will be apparent from the following specification when taken with the accompanying drawing, in which Fig. 1 is a side elevation of a slug employed to make a shell according to the present invention, v

Fig. 2 is a plan view of the slug of Fig. 1,

Fig. 3 is a partial side elevation of a press employed to carry out the methods according to the present invention,

Fig. 4 is a side elevation of a blankformed directly from the slug of Fig. 1,

Fig. 5 is a plan view of the slug of Fig. 4.

Fig. 6 is a side elevation of a blank formed directly from the blank of Fig. 4,

Fig. '1 is a side elevation of a blank forged directly from the blank of Fig. 8,

Fig. 8 is a vertical section disclosing the blank of Fig. 7 arranged over a water nozzle, Fig. 9 is a partial vertical section of a drawing press for performing a step in the method according to the present invention, and Q Fig. 10 is a vertical section of a blank'obtained by the press of Fig. 9, the section being lined to show the alignment of the grain structure.

Referring particularly'to Figs. 1 and 2 of the drawing, the reference character I indicates a steel slug. The slug I is of generally square cross section with the corners cut off. The slug l preferably is cut from rolled bar stock. A-cast slug would not be satisfactory because of its large grain structure. The slug l is heated to a suitable temperature in an oven and then is placed on end in a lower die 2 supported on a press bed 3. Co-operating with the die 2 is'a die 4 supported from a heavy plate 5 mounted on a press ram 8, the press ram 6 being reciprocable by suitable mechanism well understood in the art. The die 4 is moved from its dottedline position as shown in Fig. 3 down to its full line position. The dies 2 and 4 are cup-like and of frustro-conical-shape, and the die 4 is provided at the inner end thereof with a centering nub I. The action of the dies 2 and 4 is to squeeze the slug I endwise to provide a somewhat foreshortened blank 8, shown particularly in Figs. 4 and 5. The blank 8 is provided with a center notch 8 formed by the nub I in the die 4. Also as the dies 2 and 4 move together, the corners of the blank adjacent the top and bottom thereof are pressed in starting the forming of the work into a piece having a cylindrical cross section, which forming is completed in the next operation.

The blank 8 is operated on by a plug l8 sup- 8 with respect to the plug I8. The blank 8 is supported against tipping from the plug l8 by a suitable structure not shown.

The dies 2 and 4, the plug l8, and the die II, are mounted in the same press, because the operations performed by them respectively, immediately follow one another. The purpose of the dies 2 and l is to not only provide the cen tering notch 9 but also is to crack the scale that has accumulated on the slug I while in the heating oven. The compressing action of the dies 2 and 4 cracks the scale, permitting it to fall off. Any scale that forms in the die 2 escapes downwardly through the bore l2 extending through the bottom of the die 2 and the press bed 3.

While the bore [2 is of substantial diameter, the squeezing action of the slug l is not enough to force any material amount of the slug therein. The scale in the notch 8 gravitates therefrom as the blank 8 is inverted and moved into position over the plug l8. Thus a scale free blank 8 is disposed into position to be operated upon by the plug I8 and die ll. When the blank 8 has been properly positioned on the plug I8, the die H is moved downwardly under the action of the ram 5 to provide the blank [5, shown particularly in Fig. 6. The blank [5 is shown in dotted outline in Fig. 3 and is provided with a central opening l6 formed by the plug I8.

The blank I5 is freed from the plug l8 by a stripper l1 actuated by mechanism not shown but preferably from the ram 6 in a manner not shown, but disclosed in my copending application Serial No. 327,114, filed April '1, 1940, which has matured into Patent No. 2,314,148. The

blank I5 is removed from the plug l8 and shaped in a steam hammer between forging dies, not shown, to produce the conical blank I8, shown in Fig. 7.

The opening IS in the blank I5 is provided to receive the male forging die to insure the centering of the work during hammering. Without the central opening IS in the blank l5, it would not be possible to maintain the blank to be forged, centralized with respect to the forging dies, and a one sided forging would result. Likewise, if the blank 8 were not provided with the centering notch 9, it would not be possible to cause the disclosed in my copending application executed and filed on an even date herewith. The mandrel 28 is actuated by a ram 22 and is moved downwardly from the dotted line position shown in Fig. 9 to the full line position shown in Fig. 9

to force the blank l8 past the trimming die 23, which trims oil the flash 24 of the blank l8, and through the drawing die 25 to swing in the sides of the blank l8 and to draw the same into the cylindrical shell 26 shown in dotted outline in Fig. 9 and in Fig. 10. It will be understood that the flash 24" constitutesthe surplus metal from the hammering operation.

One of the important features of the press 2! which is shown in my aforesaid copending application is thed'ie 38 mounted on springs 3|, which are in turn supported on a base 32 mounted on the pressbed 33. As the mandrel 28 reaches its lower-most'position it'urges the lower end of the drawn shell 26 into the die 38 to impress the same, to smooth out any imperfections in the outlineof the end which may have resulted from wear in the forging dies, it being understood that the outside diameter of the closed end of the blank is unchanged in passing through the draw-' ing die 25. Also the die 38 may impress in the end of the shell 26 suitable identifying numbers 34, such, for instance, as the heat number of the shells being run. As will be observed from Fig. 9, the die 38 has number dies 35 in the bottom thereof.

The trimming die 23 and the drawing die 25 are supported from a table 36 suitably supported by legs 31 from the press bed 33. Employed in association with the drawing die 25 is a stripper, not shown, for stripping the shell 26 from the mandrel 28 upon its upward movement. The stripper is more particularly shown in my afore said copending application. When the mandrel 28 has been lifted from the shell 26, the shell 26 may be slightly. elevated to lift it from the die 38 and then removed from the press.

The present invention is of particular significance in that it produces a shell, which not only has small manufacturing tolerances but also upon being exploded fragmentates'into a great number of small pieces.

fined by the forging and is still further improved by the swinging in of the sides of the conical blank to provide the cylindrical shell 26.

Another one of the features of the invention is" the arrangement of the grains at the closed and fof the shell 26. By arranging the alignment of the grains in the closed end in smooth flowing curves, as illustrated particularly in Fig. 10, the

fragmentation of the shell at the closed end is would break off in a single piece or at the most in a very few pieces.

The smooth flowing curvature of the lines of grains is obtained by controlling the depth of the opening l6 in the blank IS. The depth of the opening l6 should be such that the thickness of the end wall is substantial when compared to the thickness of the side walls. Then when the blank I5 is hammered to reduce the thickness of the side and end walls and to produce the blank l8, the metal at the closed end of the blank l5 flows through a substantial distance into' the side walls of the blank l8. This flowing of the metal provides the desired grain contour illustrated in Fig. 10. To more fully understand the result I have obtained, note is made of the fact The high fragmentation obtained .in shells made according to the present invention is in a large part due to the grain structure of the shell. The grain structure is re that should the opening I6 have been so deep as to provide only a small amount of metal at-the closed end of the blank [5, the grain contours would have taken 'sharp right angle bends at the closed end of the blank 18, resulting in a generally weakened area.

The results of fragmentation tests illustrate the degree of fragmentation of shells fabricated according to the present invention. Average figures reveal that a shell weighing 10.69 pounds when empty, when loaded and exploded broke into 411 pieces, eachweighing between and 75 grains and totaling 1.805 pounds, 152 pieces weighing between '75 and 150 grains, totaling 2.655 pounds, 106 pieces each weighing between 150 and 750 grains, totaling 5.074 pounds, and two pieces weighing between 750 grains and 2,500 grains, totaling .335 pound. There were no larger pieces. The total number of fragments recovered was 6'72, weighing a total of 9.870 pounds.

The high degree of fragmentation of shells fabricated according to the present invention is due to the general grain structure provided, the alignment of the grains adjacent the closed end of the shell, and the freedom from scale during fabricating.

Another feature of the invention is the employment of a generally square slug to produce an article which in finished form is cylindrical. Should a cylindrical slug be used, there would have to be a greater fiow of metal during the fabricating steps than there is when a generally square slug is used. Hence, by employing a square slug according to the present invention, there is a saving in power and time consumed. It will be understood that while a square slug is preferred, because of the fact that it is a standard shape, slugs of other numbers of sides may be employed with beneficial results. However, within the scope of the invention, aside from the advantage of using a squared slug, a slug of any suitable form may be used.

While the invention has been described as applying to the manufacture of high explosive shells, it will be understood that it may be employed for the manufacture of other similar articles.

Having thus described my invention, what I desire to secure by Letters Patent and claim is:

1. In the manufacture of hollow objects, the steps of heating a slug, pressing a centering notch therein and at the same time slightly compressing the slug to crack scale thereon while maintaining the sides of the'slug substantially free to permit loosened scale to escape, and pressing a plug into the notch to enlarge the same and hollow the slug.

2. In the manufacture of hollow objects, the steps of heating a slug, pressing a centering notch in the top thereof, and at the same time slightly compressing the slug to crack the scale thereon, while maintaining the sides of the slug free to permit cracked scales to fall therefrom, inverting the slug while the slug still has its original heat, and pressing a plug into the notch to enlarge the same and hollow the slug, whereby any scale in the notch is permitted to gravitate therefrom as the slug is inverted.

3. In the forging of hollow objects, the steps of heating a slug, pressing a centering notch therein, and at the same time slightly compressing the slug to crack the scale thereon, pressing a plug into the notch to enlarge the same and hollow the slug, and hammering the hollowed slug to reduce the wall'thickness thereof and shape the same.

4. In the forging of hollow objects, the steps of heating a slug, pressing a centering notch therein, pressing a'plug into the notch to enlarge the samev and hollow the slug, hammering the hollowed slug to reduce the wall thickness thereof and to shape the same, and drawing the forged blank. I

5. In the forging of hollow objects, the steps of heating aslug, pressing a notch in the top thereof and at the same time slightly compressing the slug to crack the scale thereon, inverting the slug to permit the scale within the said notch to gravitate therefrom, pressing a plug into the notch to enlarge the same and hollow the slug, hammering the hollowed slug to reduce the wall thickness thereof and shape the same, and drawing the forged slug.

6. In the manufacture of tubular members such as shells and the like, the steps of forging a blank having one end open and the other end closed, directing water into the open end to crack the scale thereon while holding the forged blank with the open side thereof down, inserting a mandrel in the open end, and forcing the forged blank, by said mandrel, through a drawing die.

'7. In the manufacture of tubular members such as shells and the like, the steps of forging a blank having one end open and the other end closed, directing water into the open end to crack the scale thereon while holding the forged blank with the open side thereof down, inserting a mandrel in the open end, forcing the forged blank, by said mandrel, through a drawing die, and-pressing the closed end against a die by said mandrel to impress the closed end as desired.

8. The method of drawing a hollow, heated blank having a closed end and an open end which comprises directing water into the open end of the blank to crack scale thereon, disposing a mandrel in the open end of the blank, and forcing the blank, by the mandrel, through a drawing die;

9. In the manufacture of heavy tubular members such as shells and the like, the steps of heating a blank, pressing a center notch in one end thereof, pressing a plug into said notch to at least partially hollow said blank, hammering said blank to shape the same, drawing the hammered blank'by a mandrel to elongate the same, and pressing the closed end of the drawn blank by, the mandrel against a resiliently mounted die to impress said end as desired.

10. In the manufacture of tubular members such as shells and the like, the steps of heating a slug, pressing a centering notch into the top of the slug and at the same time compressing the slug to crack the scale thereon, inverting the slug, pressing a plug into the notch to enlarge the same and hollow the slug, forging the hollowed slug to provide a blank of a predetermined wall thickness and configuration, directing water into the open end of the blank while supporting the blank with its open end downwardly, inserting a mandrel inthe open end of the blank, forcing the blank, by said mandrel, through a drawing die, and pressing the closed end of the drawn blank against a die by said mandrel to impress the closed end as desired.

11. In the forging of hollow objects, the steps of heating a slug, pressing a centering notch therein, and at the same time slightly compressing the slug to crack the scale thereon, pressing a plug into the notch to enlarge the same and hollow the slug to provide a member having side walls and an end wall, the end wall being of substantial thickness as compared to the thickness of the side walls, and hammering said member between forging dies to reduce the thickness of said walls and to provide said member with a predetermined shape.

12. In the manufacture of heavy tubular members such as shells and the like, the steps of heating a blank, pressing a center notch in one end thereof, pressing a plug into said notch to at least partially hollow said blank to provide a member having side walls and an end wall, the

end wall being of substantial thickness as compared to the thickness of the side walls, hammering said member between forging dies to reduce the thickness of said walls and to provide. said member with a predetermined shape, and drawing the hammered blank to elongate the same.

13. In the manufacture of hollow objects, the steps of heating an elongated slug of polygonal cross section and slightly compressing the same longitudinally, and laterally against at least parts of the portions thereof at which the side faces intersect, for cracking the scale on the slug.

ALIDOR IEFERE. 

